March 4, 2009 -- Around the world, increasing numbers of male fish are developing female traits -- growing new sexual organs and sometimes even producing eggs. The phenomenon has been blamed mostly on chemicals that get into the water and mimic the female hormone estrogen. But a new study puts some of the blame on an entirely different class of chemicals -- ones that block the action of male hormones called androgens. It isn't the first study to suggest that anti-androgens might be contributing to the feminization of fish. But the new research found that there are far more of these chemicals in our lakes and streams than anyone realized. And anti-androgenic chemicals in the water might affect human health as well. "They are going to be some potent players," said Charles Tyler, an ecotoxicologist at the University of Exeter in England. "It is possible that there are going to be many more chemicals that are anti-androgenic than are estrogenic." Related Content:
Tyler, along with Susan Jobling at Brunel University in London and other colleagues, looked at chemical run-off in 51 rivers throughout the United Kingdom. By combining concentrated water samples with cultures of yeast genetically engineered to have androgen receptors, the scientists were able to measure the amount of anti-androgen activity in each sample. The researchers' results, published in the journal Environmental Health Perspectives, revealed a significant amount of anti-androgenic activity in nearly all of the samples tested. The researchers also collected fish from each site. With statistical models, they were able to show that anti-androgens were just as responsible for the feminization of fish as estrogenic compounds were -- if not more so. "The amount of anti-androgen activity is pretty much a surprise," Tyler said. "We expected some, but nowhere near the level of potency we found." Get More NewsSpiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates.Oldest Hebrew Writing Possibly FoundAncient inscriptions on a 3,000-year-old pottery shard could make history.Rare, Prehistoric-Age Reptile Found in N.Z.A tuatara has been spotted on the New Zealand mainland for the first time in 200 years.Iceman Has No Living RelativesOetzi, the 5,300 year-old frozen mummy, left no living genetic legacy.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.It's Official: People Are Warming the PolesHumans are conclusively to blame for polar warming, say scientists.Eight-Armed Animal Preceded DinosaursWhat may be one of Earth's first animals was no bigger than a coaster and had eight arms.Phoenicians Live on in People's GenesOne in 17 Mediterranean men may be descended from ancient Phoenicians.Pesticides, Fertilizers Linked to Frog DeclineA pesticide is found to promote parasites among amphibians.Hubble Telescope Taking Photos AgainThe Hubble Space Telescope is once again snapping stunning photos of the universe.Andean Mummy Hairs Show Hallucinogen UseScientists find direct evidence of hallucinogenic drug use among ancient Andeans.Opals on Mars Reveal Planet's Long Wet PastOpals found on Mars suggest the planet has been wet for much longer. |
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